Illuminating device for simulating daylight



Dec. 22, 1925- 1,566,703 A. R. ST. CLAIR ILLUMINATING DEVICE FOR SIMULATING DAYLIGHT Filed Jun 20. 1925 sTR/Ps 0F mvrsn GLASS \{PLA/N FRDJTED GLASS wmwz'm: PrFurr Regindd 6r. Chair.

AUWEY Patented Dec. 22, 1925.

- UNITED STATES ARTHUR REGINALD ST. CLAIR, OF WHITLEY BAY, ENGLAND.

ILLUMINATING DEVICE FOR SIMULATING DA YLIGHT.

' Application filed june 20, 1925. Serial 180.- 38,537.

To all whom it may concern:

Be it known that I, ARTHUR REGINALD 'ST. CLAIR, a subject of the King of Great Britain and Ireland, residing at Arnclifi'e, Waterford Crescent, Whitley Bay, in the county of Northumberland, England, have invented certain new and useful Improvements in Illuminating Devices for Simulating Daylight. and for which I have filed appllcation in Great Britain, Nov. 30, 1923, of which the following is a specification.

This invention relates to illuminating de- 'vices, and has for its object to provide a device which may be applled to existing metal filament electr1c lam s, arc lamps or incandescent gas lampsereinafter referred to generally as lampsso as to produce a light which will allow of the accurate oomgparison of colours, will lessen the glare eflffect of such lamps, and will generally be of similar quality to daylight.

This object is attained according to the present invention by providing a light filter through which the rays of the lamp are caused to pass, said filter comprising a translucent medium such as glass, mica, or the like, having a tint known in the coloured glass trade as Cobalt blue.

As the tints of glass vary with the different makers, the limits of shades between which the desired results will be attained, are best defined according to the anal ses given by Lovibonds tintometer. According to the readings of this instrument, the tint may vary between blues of the following analyses :.Blue 3.5, red 0.05, and blue 6.0, red 0.50. q

For matc'hing'colours the hest results are obtained by rovidin a white frosted glass next to the lter medium the tint of which is preferably :--Blue 4.10 and red 0.20, according to the above standard. Alternas tively, the filter medium itself may be frost, ed, and in the case of a glass filter the'most su1tab1e frosting is that obtained by the treatment known as acidating, this'treatment giving a finer frost than that ohtamed by the sand-blast treatment. Again, in the case of an electric li ht.bulb, the bulb itself maybe "frosted, pre erably by acidatin and the filter medlumoleft plam.

In one form of the device according to the present invention, the filtercomprises a plate. of glass of Ifpobalt blue tint according to the above-for ula, and a plate of white parabolic, for example. The 0 frosted glass, both plates being ofabout the thickness of window glass. The said plates are held together, for example by means of lead strips bent over the edges ofthe two plates, and the resulting composite filter is Inserted in a detachable manner into the opening of an opaque shade adapted to fit ventilation apertures are provided at the upper and lower'portions of the shade to allow of the circulation of air. Preferably, similar apertures are provided on the device for use with electric lamps in order to prevent the deposit of moisture on. the glass. Further, additional apertures or perforations may be formed adjacent the edge of the filter in order to prevent overheatin'gof the latter. y o

The single figure of the accompanying drawing is a sectional view of the bottom part of a lamp equipped with the invention.

Referring more articularly to the draw ing, A indicates tie cylindrical portion of the lamp casing havinggan internal flange there is a yielding packing C, the filter resting on said packmg. The filter comprises a single tinted glass D divided into stripsto prevent cracking-through overheating, and a plain frosted glass 1) underneath, also in strips which are arranged at right angles to those of the tinted glass D. The two glasses are held together by a rim E of soft metal such as lead or zinc.

I claim I 1. A light filter for use with artificial light comprising a translucent medium having a tint lying between the following analyses according to' Lovibonds tintom- 'eterr-Blue 3.50, red 0.05, and blue 6.0,

-red 0.50.

2. A light filter for use with artificial light comprising a translucent medium hav- A formed at its lower end, on which flange in to Lovibonds tintometerz -Blue 4.10, re 0.20.

3. A light filter for use with artificial light comprising a plurality of strips of translucent lass having a tint lying between the 0 lowing a lyses according to Lovibonds tintometer': lue 3.50, red 0.05, and blue6.0, red 0.50, and a plurality of strips of frosted glass placed against said stris of translucent glass, the strips of the ion element being set at an angle to those if? the other element.

4. A light filter for use with artificial light comprising a plurality'of strips of translucent glass havin a tint'of the following analysis accor in to Lovibonds tintometer:-Blue4.10, re 0.20, and a plurality of strips of frosted glasspla'ced against said strips of translucent glass, the strips of the one element being set at an angle to those of the other element.

In witness whereof I have signed this specification.

ARTHUR REGINALD ST. CLAIR. 

